I have four 5-poles in the back half of the retopology.
Poles are not bad at all. In fact, I'd be surprised if you didn't use at least three in the back. They're a way of guiding edge flow smoothly and to where you want them to go. If you haven't done the Blender Modeling Bootcamp, I'd suggest you do this before going on to more complex concepts like sculpting and retopology.
Good luck!